fix: Leading element in .proj sexp

Pantograph/Serial.lean

@@ -155,7 +155,7 @@ partial def serialize_expression_ast (expr: Expr) (sanitize: Bool := true): Meta
 
       let autos := String.intercalate " " (List.replicate ctor.numParams "_")
       let inner ← self inner
-      pure s!"(:app (:c {projectorName}) {autos} {inner})"
+      pure s!"((:c {projectorName}) {autos} {inner})"
   -- Elides all unhygenic names
   binder_info_to_ast : Lean.BinderInfo → String
     | .default => ""

Test/Serial.lean

@@ -74,7 +74,7 @@ def test_sexp_of_expr (env: Environment): IO LSpec.TestSeq := do
             .default)
         .implicit)
       .implicit,
-      "(:lambda p (:sort 0) (:lambda q (:sort 0) (:lambda k ((:c And) 1 0) (:app (:c And.right) _ _ 0)) :implicit) :implicit)"
+      "(:lambda p (:sort 0) (:lambda q (:sort 0) (:lambda k ((:c And) 1 0) ((:c And.right) _ _ 0)) :implicit) :implicit)"
     ),
   ]
   let termElabM: Elab.TermElabM LSpec.TestSeq := entries.foldlM (λ suites (expr, target) => do